To my mind, crab ravioli calls for a creamy sauce on the white/light side. A simple dab of creme fraiche (maybe cheeseandchocolate -- see post further down -- could spare a little) with a few capers and a few good grinds of black pepper....Beurre blanc (try a basil beurre blanc?)....reduce a little Pernod with a few minced shallots, dose in a little heavy cream & let that reduce, season with S&P....Beurre noisette and a squeeze of lemon with some snipped chives....ummmmm somebody stop me......

I second the tomato cream sauce - the tomato balances out the richness of the crab and cream. I would suggest topping the dish with a bit of fresh diced tomato and basil chiffonade - perhaps a little lemon zest for freshness. Sounds fantastic!